The invention relates to a method and to a processor for classifying data packet units. Data networks have various switching principles, i.e. the way in which data streams are forwarded between the communication devices connected to the network.
Line detection involves the communication units being connected by connecting lines together. In this context, the subscribers are directly connected to one another after the connection has been made.
In contrast, communication involves the data which are to be transmitted being transferred on the basis of their destination address from the source node via intermediate nodes, i.e. switching centres. A special form of message transmission is what is known as packet switching. In this case, the data to be transferred are split into fragments of particular length, are provided with control information, including address information, and are sent. The addressed data fragments are called data packets or data packet units. Data networks based on packet switching technology are called packet switching networks or packet switching data networks. The data packets or data packet units (DPU) are forwarded from switching node to switching node without first needing to wait for all the data packets associated with the data record in question to be received. The data packets may also be sent from the sender to the receiver on different transmission routes. In the event of errors occurring on account of faults, packet switching technology requires only the erroneous data packet to be resent and not the entire message. Packet switching networks have a good utilization level for the connecting lines on account of the possibility for the data packet streams to be able to be routed through the network on different routes in line with the data network's load situation.
The data packets are forwarded to the data network using network processors. FIG. 1 shows a conventional network processor. The network processor firstly has input ports E and secondly has output ports A. The maximum data width of data which can be transmitted digitally by the ports is dependent on the width of the data bus. Typically, the ports are actuated by means of an associated port register. Ports can transmit data both unidirectionally and bidirectionally.
FIG. 2 shows the data format of a conventional data packet unit or of a conventional data packet. The data packet firstly comprises useful data or payload and secondly comprises data packet management data or a header.
The data packet management data or header data typically comprise a transmission protocol, a destination address DA for the data packet, a source address (SA) and possibly one or more indicator tags. The communication protocol or transmission protocol comprises agreements and conventions on the basis of which the communication between subscribers is effected. The OSI reference model is an architectural model from the International Standards Organization (ISO) for data communication in open systems OSI (Open Systems Interconnections). The OSI reference model comprises seven layers: the application layer, the presentation layer, the session layer, the transport layer, the network layer, the data link layer and finally the physical layer. Each layer has an associated transmission protocol which is compatible with the adjoining layers.
In the network layer, the data packets are transported through the network using the techniques of “switching” and “routing”. The network layer also makes the logical associations for remote computers, performs the addressing, connection of various networks (Internet working), error handling, data congestion control and the categorization of data packets into data streams. In the data link layer, the transmission control for data units (frames) is effected on transmission sections between the nodes of communication networks. Known data transmission protocols include Ethernet, IP, PPP, HDLC or the ATM data transmission protocol. The quality of service QoS indicates the collective effect of a service, which determines the degree of satisfaction of a service user. Typical QoS criteria are availability, the probability of loss and error for data packets, the delay time for data packets as a result of congestion and overload phenomena in the data transmission network, the propagation time for the data packets and also their jittering, and the degree of data compression and pause suppression. The quality of service therefore refers to all factors which influence the quality of service, for example network down times, bit error rates on channels, delay times for connection setup, stability of the connection and probability of blocking. The QoS is defined in different ways for different services and networks.
The data packets arriving on the input ports of the network node or network processor are subjected to classification by the network processor. Such classifications relate inter alia to the determination of an output port, the quality of service QoS for the data packet, the identification of special data packets and also the insertion of data fields into the data packet. In the case of conventional classification methods, data packets which have certain properties or data packet parameters are handled in prioritized fashion.
Data packets have firstly data parameters with explicit indications in the data packet management data, such as destination and source addresses, and secondly implicit data packet parameters or data packet properties, such as the arrival time of the data packet on one of the input ports of the network processor or the port number of the input port.
In conventional methods for classifying data packet units, classification is effected using a data packet parameter. By way of example, the quality of service is allocated on the basis of the implicit data packet parameter “input port number”. In other methods, classification is effected on the basis of indicator tags, such as a Layer-2 tag like VLAN or a Layer-3 tag like TOS. In addition, conventional methods for classifying data packet units involve the classification algorithm being prescribed and nonconfigurable.